my %seen;
my @array = grep !$seen{$_}++, LIST;

##</code><code>##

my %seen;
my @array = grep !$seen{$_}++, @array, $new_value;

##</code><code>##

my %edges;
while (<STREAM>) {
   my($node1, $node2) = split;
   my %seen;
   @{$edges{$node1}} = grep !$seen{$_}++, @{$edges{$node1}}, $node2;
}

##</code><code>##

my %edges;
my %seen;
while (<STREAM>) {
   my($node1, $node2) = split;
   next if !$seen{$node1}{$node2}++;
   push @{$edges{$node1}}, $node2;
}